Upwork Inc. (NASDAQ:UPWK) stock tumbled in premarket trading on Tuesday after the freelancing platform issued disappointing first-quarter guidance despite beating Wall Street estimates for its fourth-quarter results.Q4 Results Top ExpectationsUpwork reported fourth-quarter revenue of $198.41 million, beating analyst estimates of$197.52 million. The company posted adjusted earnings of 36 cents per share, surpassing estimates of 31 cents per share.Soft Q1 Outlook Weighs On SentimentUpwork expects first-quart ...